This research is aimed toward understanding mechanisms involved in the regulation of expression of insulin and glucagon receptors in cultured fibroblasts from control and diabetic animals and humans. To attain this, we plan to study the kinetic and immunocytochemical characterization of insulin and glucagon receptors in control cells and possible alterations in diabetic cells. It is proposed to investigate the mechanism of "down-regulation" of insulin receptors by insulin using techniques such as specific radio and photolabelling of the receptors, and reaction with specific antireceptor immunoglobulins. Distribution of microtubules and microfilaments related to the expression of hormone receptors will be studied by immunocytochemical and immunofluorescent analysis of cells treated with agents which disrupt these cytoplasmic structures. Effort will also be directed toward understanding the mechanisms underlying the regulation of post-receptor responses of insulin and glucagon (including nutrient transport, DNA synthesis, ODC activity and adenylate cyclase activity) after they interact with their receptors at the cell surface. Studies will be directed toward identifying alterations at the cellular level which are causally associated with diabetes mellitus.